Getter assembly



Nov. 17, 1936. J. GLANS 2,060,561

GETTER ASSEMBLY Filed Sept. 29, 1934 INVENTOR JOSEPH GLANS ATTORNEY Patented Nov. 17, 1936 UNITED STATES GETTER ASSEMBLY Joseph Glans, Bloomfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 29, 1934, Serial No. 746,165

4 Claims.

My invention relates to electron discharge devices and to improvements in means for introducing vaporizable clean-up agents or getters into the device during the process of manufacture, and more particularly to improvements in the getter holder or getter assembly and a meth- 0d of making it.

The conventional method of providing a high vacuum in an electron discharge tube comprises exhausting the tube quite thoroughly by a pump and then removing the greater part of the residual gases by combining them with a metallic clean-up agent or getter, such as magnesium, which is vaporized or flashed within the tube. The getter is usually attached to a metal getter tab mounted in the tube, and. heated by means of a high frequency induction coil during the exhaust of the tube until the heat conducted to the getter from the tab vaporizes the getter.

The conventional getter assembly comprises a sheet metal tab provided with a shallow cup or recess in which the getter, usually in the form of a pellet, may be placed. A getter retainer, usually a metal screen, is placed over this pellet and welded to the sheet metal tab at three or four points near the edge of the screen to hold the getter pellet in place.

A getter assembly of the type described is usually assembled by hand, hence the welds are not always uniform and the getter retainer is not tightly drawn against the getter pellet and may even be loose at one or more of the edges. The resulting loose contact between the getter pellet, the getter retainer and the sheet metal of the tab may result in such poor heat conduction between the getter pellet and the tab, that the high frequency heating of the getter tab causes only partial vaporization or flashing of the getter pellet, which produces a poor vacuum. A getter retainer loose at the edge may permit pieces of the getter pellet to be blown out during the high frequency heat treatment and to form on the interior surface of the glass envelope socalled getter spots, which often weaken the glass to such an extent that the glass may be easily punctured at the getter spots.

Another disadvantage in the use of a getter assembly having a mesh or screen getter retainer welded to the getter tab is that such a screen may fray at the edges and parts of it may drop into the tube and lodge across the terminals of the electrodes, or between the electrodes, causing a short circuit in the tube and damaging not only the tube in which such a getter assembly is used but also associated equipment.

- One object of my invention is to provide an improved form of getter assembly in which the getter will always be properly flashed, insuring proper gettering of the tube and elimination of getter spots with the resultant damage to the Walls of the tube envelope. Another object of my invention is to provide an improved and simplified getter assembly which eliminates the objectionable characteristics of assemblies using screen retainers for holding the getter pellet on the tab. A further object of my invention is to provide a getter assembly which can be made entirely by automatic machinery, thus eliminating the poor construction and variations which may occur-in hand-manufacture. A still further object of my invention is to provide a novel method of making the improved getter assembly.

. In the preferred embodiment of my invention the getter assembly comprises a sheet metal tab shaped to form a cup in which the getter pellet is very firmly held or clamped by a rigid metal retainer in the form of a mesh plate having a plurality of holes punched therein, the rim of the cup being inturned or curled in over and down on the edges of the retainer to .press the retainer firmly against the getter pellet and clamp the pellet between the retainer and the bottom of the cup. In this way a getter assembly is produced which is simple and rugged and in which the getter pellet is firmly clamped to the metal of the tab which gets hot when the tab is heated by high frequency induction, so that the vaporization of the getter is facilitated. The getter assembly can be made easily and rapidly by automatic machinery, and is so rugged that it cannot be injured by rough handling or usage in the factory.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 is a plan View of a getter assembly made in accordance with my invention; Figure 2 is a side edge view of a getter assembly shown in Figure 1, Figures 3 to 6 inclusive show various steps in the formation of the getter assembly shown in Figures 1 and 2, and Figure 7 is an enlarged perspective view in section showing details of construction of the assembly shown in Figures 1 and 2.

In the getter assembly shown in Figures 1, 2

and 6, the getter tab I0, made of sheet metal, preferably nickel, is shaped to have a cup-shaped depression or recess slightly larger than the getter pellet and encircled by an annular shoulder [2. The getter pellet I3 is held in the recess in the bottom of the cup by means of a getter retainer [4, preferably a rigid disc of sheet metal perforated with a number of holes formed by punching and of such size that it fits into the cup and rests on the annular shoulder I2. The

disc I4 is preferably placed in the cup, as best.

shown in Figure '7, with the side roughened when the holes are punched in the metal resting onthe getter pellet, and the protruded ridges or projections i5 raised by punching-the holes extending into the getter pellet. The sheet metal around the shoulder I2 is drawn up to form the side or annular wall l6 of the cup and is-folded over the edge of the disc retainer l4 and the shoulder [2 to securely grip the edge of the disc and force the retainer HI down against the getter pellet to clamp the getter pellet against the bottom of the cup ll in-the tab l0. Flutes H in the getter tab may be provided to facilitate positioning the welding of support wires to the tab.

It has been found that if the retainer is formed of mesh plate having punched holes from .005 to .010 in diameter, with their centers spaced approximately apart, very good results are obtained. If the holes are too large and the spacing too great getter spots will begin to appear, whereas if the'holes are made too small and too close together an insufficient amount of the v getter will be flashed into "the tube. Punched sheet metal having several hundred holes per square inch has been foundvery-satisfactory. It is believed that forcing the projecting punched portions ofthe mesh disc into thegetter pellets assists in the conductionof heat-to the pellet so that flashing is facilitated. The-holes in the retainerdisc are so small-that solid particles cannot be thrown-out of the getter assembly when the pellet is flashed, so thatonly the-completely vaporized getter leaves the assembly.

The method of making the getter assembly-is shown in Figures 3 to-6 inclusive. The sheet material of which the getter tab H) is made,- is drawn to shape, as shown in Figure 3, to form the cup H with the annular shoulder-l2 and the annular side or wall -l6. The getter-pellet -I3 is then placed in the recess in the bottom of'the cup II and the perforated punched-- metal retainer placed over the pellet with the rough side against the pellet and with its projecting punched portions resting on the pellet. The-vertical annular wall I6 is then folded over the edges of the disc to press thedisc against theshoulder l2, as shown in Figure 4, and thereby securely grip the edges of the retainer and force the rigid retainer down in place against the getter pellet. This operation forces the rough side of the punched metal disc down into the getter pellet and securely clamps the getter pellet between the bottom of the cup and the rigid-disc retainer, the pressure of the retainer against the pellet in the finished article being equal to the maximum pressure produced during assembly.

All of the above operations canbe performed automatically by machine, thereby eliminating the necessity for any manual operations inconnection with the manufacture of the getter assembly. If the retainer disc is made of woven wire mesh .or screen thisimproved' method eliminates any necessity for welding, and prevents any raveled ends of the screen dropping off intd the tube, since the raw edges of the screen or the mesh retainer are securely clamped between the shoulder l2 and the folded-over or inturned walls I6 of the getter tab.

A getter assembly made in accordance with my invention can be easily made and eliminates the objectionable features of the usual getter assembly employing a screen welded to the getter tab for holding the getter in place. The getter .assembly can be made automatically, and thus more uniformly, and better controlled flashing is obtained.

.While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific aplication for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is 1. A getter assembly comprisinga sheet metal tab having a cup-shaped depression, a getter pellet of substantially the same thickness as the depth. of said depression in said cup-shaped depression, a metal plate having a plurality of inwardly punched holes therein with protruded ridges positioned over and-in contact with said getter pellet, the sheet metal tab'being. secured to the .metal plate to clamp the. getter pellet between .the bottom of said cup-shaped depression andsaid metal plate, the pressure exerted by said rigid metal plate onsaid getter pellet being sufficient to embed said ridges in the pellet.

2. A getter assembly comprisingv a sheet metal tab having a cup-shaped depression provided with .an outwardly extending shoulder, a getter pellet in said cup-shaped depression, a .rigid metal ,disc having a plurality of punched holes positioned over and in contact with said getter pellet with the punched portions of the rigid metal disc-extending into the surface'of said getter pellet, the sheet metal .tab beingdrawn and folded :in over the edges -.of said metal. disc againstsaid shoulder to grip the edge, of said rigid metal-disc and to draw said rigid metal .disc down against said getter pellet whereby said getter pellet is clamped to the bottom of said cupshaped depression.

.3. In a getter assembly, a container comprising a cup-shaped member with a closingplate, a. getter ,insaid member, the closing plate being secured .to the member to firmlypress said getter against the inner surfaces of said member, a plurality of perforations insaid container to permit theescape of vapors, and .a plurality of metallic protrusions extending inwardly from the inner surface of said container to provide good heat conducting paths from said container .into said getter.

4; A getter assembly comprising a sheet metal tab having .a cup-shaped depression, a getter pellet in said depression, a metal plate having a plurality of perforations over said pellet and secured to said tabto clamp the getter pellet between the bottom of said cup-shaped depression and the metal plate, interiorly extending "protrusions integral =with-said plate to embed in the pellet.

'JOSEPH GLANS. 

